北京邮电大学通信原理课件--第4章-模拟通信系统

4.1()sin2mmtftπ=()sin2cctAcftπ=DSB-SC6cmff=(1)DSB-SC(2)DSB-SC(3)(1)()()()(()()()sin2sin2sin2sin12cmccmstmtctAftftAftftππππ===)m(2)()st()()cos10cos142cmmAstftftππ=−()()()(()55774cmmmASfffffffffδδδδ=−++−−−+⎡⎤⎣⎦)m(3)4.2()()()444coscos2.410()cos2102.210ttstπππ++=×××4tAM(1)(2)()st()Lst(3)(4)(1)()st1/251()()()()()()()3333311010101021110111021121012102Sfffffffδδδδδδ⎡⎤⎡=+×+−×++×+−×⎣⎦⎣⎡⎤++×+−×⎣⎦3⎤⎦1110KHz12KHz1KHzKHz()34cos2210tπ×(2)()st()Lst()()()()100041000LSffffδδδ=+++−()42cos2000Ltstπ=+(3)()(){}()2Re410.5cos2000cos2cjftLcststetftπππ==+0.51KHz(4)4.3()()1cos2cos2mcstAftftππ=+fm=5KHzfc=100KHzA=15(1)(2)(3)(1)1cos2m0Aftπ+≥A=15(2)2/252(3)4.4()()()(()2cos2cos22sin2sin2mcmstftftftftππππ=−)c()2cos2mftπ=cmt()f(1)(2)(3)(4)()mt(1)()()2cos2cmstfftπ+=⎡⎤⎣⎦()()()cmcmSfffffffδδ=+++−−(2)(3)(4)()mt(cos2cft)πϕ+()()()(){}()(){}221ˆˆReReccjftjftjstmtjmtemtjmteeπϕπϕ+=+=+⎡⎤⎡⎤⎣⎦⎣⎦()()(){}()()ˆˆRecossinjmtmtjmtemtmtϕϕϕ′=+=−⎡⎤⎣⎦()()()()()()()()()()()()ˆˆˆcossincossinˆcossincossinˆjmtjmtmtmtjmtmtmtjjmtjmtjmteϕϕϕϕϕϕϕϕ′′+=−++⎡⎤⎡⎣⎦⎣=+++=+⎡⎤⎣⎦ϕ⎤⎦()mt′cos2cftπ3/253()()(){}()(){}222ˆˆReReccjftjftjstmtjmtemtjmteeππϕ′′=+=+⎡⎤⎡⎤⎣⎦⎣⎦co()mt′s2cftπ()mt(cos2cft)πϕ+4.5100cA=800KHzcf=()cos20002sin2000mtttππ=+(1)()mtHilbert()ˆmt(2)(3)(1)cos200tπHilbertsin200tπsin2000tπHilbertcos200tπ−()cos20002sin2000mtttππ=+Hilbert()ˆsin20002cos2000mtttππ=−(2)()()()()()()()()()(()3333333ˆ()cos160010sin1600102250cos20002sin2000cos16001050sin20002cos2000sin16001050cos2000cos160010sin2000sin160010100sin2000cos160010cos20ccAAstmttmtttttttttttttππππππππππππππ=+=++−⎡⎤=+⎣⎦+−×××××××()()()33300sin16001050cos279910100sin279910ttttππππ)t⎡⎤⎣⎦=××−×××(3){}cosRejxxe={}sinRejxxje=−{}*Re2zzz+=()()()(){}(){}()(){}()()()(){}333333327991027991027991027991027991050cos279910100sin27991050Re100Re250Re12251212jtjtjtjtjtstttejejejejeπππππππ××××××××−××=××−××=+=+=++−()()()()()332512799101279910Sfjfjfδδ⎡⎤=+−×+−+×⎣⎦()()()332557991079910Sfffδδ⎡⎤=+×+−×⎣⎦4/2544.6SSB-AMfc=455KHz(1)A(2)A()mt()ˆmtHilbert222cA=(1)A()(44ˆˆ()()cos2()sin2()cos9110()sin9110ccstmtftmtftmttmtt)πππ=−=×−×πB()()()()()()()()()4244444()cos9110ˆ()cos9110()sin9110cos9110ˆ1cos18210sin1821022Bststtmttmttttmtmtttππππππ=×=×−××⎡⎤=+×−×⎣⎦πC1()()2Cstmt=D()()()()()()()()()444244()sin9110ˆ()sin9110cos9110()sin9110ˆsin182101cos1821022Dststtmtttmttmtmtttπ4πππππ=×=××−×⎡⎤=×−−×⎣⎦E1ˆ()()2Estmt=−F()1ˆˆ()()22Fmtstmt=−=5/255G()()Gstmt=(2)AA()()44ˆ()()cos2()sin2ˆ()cos9110()sin9110ccstmtftmtftmttmttππππ=+=×+×B()()()()()()()()()4244444()cos9110ˆ()cos9110()sin9110cos9110ˆ1cos18210sin1821022Bststtmttmtttmtmtttππππππ=×=×+××⎡⎤=+×+×⎣⎦C1()()2Cstmt=D()()()()()()()()()444244()sin9110ˆ()sin9110cos9110()sin9110ˆsin182101cos1821022Dststtmtttmttmtmtttπ4πππππ=×=××+×⎡⎤=×+−×⎣⎦E1ˆ()()2Estmt=F()1ˆˆ()()22Fmtstmt==−G()0Gst=G()mt4.7VSB7(a)BPFH(f)7(b)6/256abW()rt()(){}2RecjftLrtrteπ=()Lrt()rt2coscftπ2()rt()(){}ReLytrt=()rtDSB()()cos2cstAmtftπ=DSB()Hf()st()()LstAmt=()()LSfAMf=()Hf()()20cLWHfffWHfelse⎧+−⎪=⎨⎪⎩()rt()Lrt()()()LLLRfHfSf=()(){}()()Re2LLLrtrtytrt∗+==()()()()()()()()()()*11222LLLLLLYfRfRfAMfHfAMfHfAMfHfHf∗∗⎡⎤⎡=+−=+−⎤⎣⎦⎣⎡⎤=+−⎣⎦⎦()Hf()()*1LLcHfHf+−=7/257()()2AYfMf=()()2Aytmt=4.8(6()10cos2104cos200sttt)ππ=+×()21050W2sP==()max1max4cos200400Hz2dftdtππ⎧⎫∆==⎨⎬⎩⎭()mtFK()4cos2002tFtKmdππτ−∞=∫τ()400sin200FmttKπ=−()mt100Hzmf=max4fmffβ∆==2(1)25100Hz1000HzfBWβ=+==××4.9f(()100cos24sin2cstftftππ=+)mc=10MHzfm=1000Hz(1)FM()st(2)fm(1)(3)PM()st(4)fm(3)(1)()4sin22tmFftKmdππττ−∞=∫()4000cos2cos2000mmFmtAfttKππ==()maxmax40004000HzFFFfKmtKK∆==×=max400041000fmffβ∆===8/258()()max224000100010000HzmBff=∆+=+=(2)mf2000Hz400022000=()24000200012000Hz+=(3)()4sin2mpftKmtπ=()4sin2000PmttKπ={}max4sin24Pmftβπ==()max1max4sin244000Hz2mmdfftdtππ⎧⎫∆===⎨⎬⎩⎭f()max210000HzmBff=∆+=(4)()()4100cos2sin4100cos24sin4cpmcmpstftKftftftKπππ⎛⎞=+×=+⎜⎟⎜⎟⎝⎠π4fβ=()max1max4sin488000Hz2mmdfftdtππ⎧⎫∆===⎨⎬⎩⎭f()()max2228000200020000HzmBff=∆+=+=4.100K()mtcf()mt()()()()(12345,,,,ststststst)a9/259()()()1ˆcos2sin2ccstmtftmtftππ=+SSB()()()2coscos21cos2ccmtstmtftKftKftKcπππ⎡⎤=2+=+⎢⎥⎣⎦AM3()()11()()1cos2()()cos2sin2cos2sin2cos2cossinsin2ttcccttcctcmdmdKKmdmdKKKftmdKcstKftftKftftftftττττττττπττπππππ−∞−∞−∞−∞−∞π⎡⎤⎡⎤⎢⎥⎢⎥⎢⎥⎣⎦⎢⎥⎣⎦⎡⎤⎛⎞⎛⎞≈−⎜⎟⎜⎟⎢⎥⎝⎠⎝⎠⎣⎦⎡⎤=+⎢⎥⎣⎦=−=−∫∫∫∫∫()()4cos2tcpstftKmdπττ−∞⎡⎤=+⎢⎥⎣⎦∫(FM)()()()5cos22cos22tcfcfdmstftKdftKmtdτππτππτ−∞⎡⎤⎡⎤=+=+⎢⎥⎣⎦⎣⎦∫(PM)4.11()()cos2cstmtftπ=()sPf4.11(a)()st02N()wnt4.11(b)a4.11(a)()mtW()st10/2510()02ssPPfdfP∞−∞==∫W()mtMP()()cos2cstmtftπ=12sMPP=04MPNW=LPF()2mt04MPPW=BPF()()()cos2sin2ccsntntftntftcππ=−()()(),,csntntnt0022nPNWNW=×=LPF()2cnt042nPNW=0000212oPWPSNNNW⎛⎞==⎜⎟⎝⎠4.12()mt10KHzW=()2maxMmtPMP540KW80dB()mt100102N−=W/Hz(1)SSB(2)0.85(AM)()stRP384401010410WRP−−=××=×(1)SSB()()()ˆcos2sin2ccstAmtftAmtftππ=+cf()ˆmt()mtHilbertHilbert()mt()ˆmtMP22222MMRMAPAPPA=+=P11/2511[],ccfWf−BPF()()()cos2sin2ccsntntftntftcππ=−()()(),,csntntnt1046021010210WnPNW−−==××=×()()cAmtnt+246410200210MSSBnAPSNP−−×⎛⎞===⎜⎟×⎝⎠23dB(2)AM()()1cos2ncstAamtftπ=+⎡⎤⎣⎦0.85a=()()()maxnmtmtmt=()nmt()2max15nMMPPmt==[],ccfWfW−+BPF()()()cos2sin2ccsntntftntftcππ=−()()(),,csntntnt10460222101041nPNW0−−==×××=×()()1ncAamtnt++⎡⎤⎣⎦22nMAMnAaPSNP⎛⎞=⎜⎟⎝⎠22